A distributed gateway (DGW) architecture is an enhanced network architecture proposed on the basis of an existing evolved packet system (EPS) network architecture according to an idea of separating a network control plane function from a user plane function. The DGW architecture includes a control plane gateway (C-GW) and a user plane gateway (U-GW).
The C-GW is a centralized control plane gateway, and may have two forms: (1) a single network element obtained after a control plane function of a serving gateway (S-GW) and a control plane function of a packet data network gateway (P-GW) in an existing 3rd Generation Partnership Project (3GPP) EPS network are integrated, and (2) two independent network elements that separately implement a control plane function of an existing S-GW (Control Plane S-GW) and a control plane function of an existing P-GW (Control Plane P-GW). The C-GW is specially configured to process control plane signaling in the 3GPP EPS network, including signaling related to functions such as mobility management, session management, address management, path management, and accounting management. The C-GW interacts with the U-GW to implement control and management on user plane data processing.
The U-GW is a distributed user plane gateway. Corresponding to the two forms of the C-GW, the U-GW may also have two forms: (1) a single network element obtained after a user plane function of the S-GW and a user plane function of the P-GW in the existing 3GPP EPS network are integrated, and (2) two independent network elements that separately implement a user plane function of the existing S-GW (User Plane S-GW) and a user plane function of the existing P-GW (User Plane P-GW). The U-GW is specially configured to process user plane data in the 3GPP EPS network, including functions such as routing and forwarding, data packet check, data packet counting, and quality of service enforcement. The U-GW processes user plane data under control and management of the C-GW. In consideration of a feature that the U-GW can be deployed in a distributed manner, the U-GW may also be referred to as a D-GW.
In the existing EPS network architecture, service continuity is implemented by means of an anchor function of the P-GW. That is, in a moving process of a user equipment (UE) in a connected mode that performs a user plane service, user plane data of the UE is always exchanged between the current P-GW and an external data network. Because the P-GW does not change in the moving process, it is ensured that a user plane IP address does not change, to further ensure continuity of the user plane service.
The U-GW (or the D-GW) in the DGW architecture may be deployed in a distributed manner according to a service requirement, to implement local access of a user, further shorten a round trip time (RTT) of user plane data, and improve user experience. During deployment, the U-GW may be moved downwards to a metropolitan area network closer to the user and even to a base station controller. With downward movement of the U-GW, a service range of the U-GW is far smaller than a service range of the S-GW/P-GW deployed in a centralized manner in the EPS network. Therefore, a probability that the serving U-GW changes in the moving process of the UE increases.
It may be learned that in the DGW architecture, how to ensure service continuity in the moving process of the UE is a prominent problem.